path: root/lib/Dancer2/Manual/Keywords.pod

# ABSTRACT: Dancer2 DSL Keywords
package Dancer2::Manual::Keywords;

__END__

=pod

=encoding UTF-8

=head1 NAME

Dancer2::Manual::Keywords - Dancer2 DSL Keywords

=head1 VERSION

version 1.1.0

=head1 DSL KEYWORDS

Dancer2 provides you with a DSL (Domain-Specific Language) which makes
implementing your web application trivial.

For example, take the following example:

    use Dancer2;

    get '/hello/:name' => sub {
        my $name = route_parameters->get('name');
    };
    true;

C<get> and C<route_parameters> are keywords provided by Dancer2.

This document lists all keywords provided by Dancer2. It does not cover
additional keywords which may be provided by loaded plugins; see the
documentation for plugins you use to see which additional keywords they make
available to you.

=head2 any

Defines a route for multiple HTTP methods at once:

    any ['get', 'post'] => '/myaction' => sub {
        # code
    };

Or even, a route handler that would match any HTTP methods:

    any '/myaction' => sub {
        # code
    };

=head2 app

Returns an instance of the app. App is a L<Dancer2::Core::App>.

=head2 body_parameters

Returns a L<Hash::MultiValue> object from the body parameters.

    post '/' => sub {
        my $last_name = body_parameters->get('name');
        my @all_names = body_parameters->get_all('name');
    };

=head2 captures

Returns a reference to a copy of C<%+>, if there are named captures in the
route's regular expression.

    get qr{
        / (?<object> user   | ticket | comment )
        / (?<action> delete | find )
        / (?<id> \d+ )
        /?$
    }x
    , sub {
        my $value_for = captures;
        "i don't want to $value_for->{action} " . 
            "the $value_for->{object} $value_for->{id} !"
    };

=head2 cookie

Accesses a cookie value (or sets it). Note that this method will eventually
be preferred over C<set_cookie>.

    cookie lang => "fr-FR";              # set a cookie and return its value
    cookie lang => "fr-FR", expires => "2 hours";   # extra cookie info
    cookie "lang"                        # return a cookie value

If your cookie value is a key/value URI string, like

    token=ABC&user=foo

C<cookie> will only return the first part (C<token=ABC>) if called in scalar
context. Use list context to fetch them all:

    my @values = cookie "name";

=head2 cookies

Accesses cookies values, it returns a hashref of L<Dancer2::Core::Cookie>
objects:

    get '/some_action' => sub {
        my $cookie = cookies->{name};
        return $cookie->value;
    };

In case you have stored something other than a scalar in your cookie:

    get '/some_action' => sub {
        my $cookie = cookies->{oauth};
        my %values = $cookie->value;
        return ($values{token}, $values{token_secret});
    };

=head2 config

Accesses the configuration of the application:

    get '/appname' => sub {
        return "This is " . config->{appname};
    };

=head2 content

Sets the content for the response. This B<only> works within a delayed
response.

This will crash:

    get '/' => sub {
        # THIS WILL CRASH
        content 'Hello, world!';
    };

But this will work just fine:

    get '/' => sub {
        delayed {
            content 'Hello, world!';
            ...
        };
    };

=head2 content_type

Sets the B<content-type> rendered, for the current route handler:

    get '/cat/:txtfile' => sub {
        content_type 'text/plain';

        # here we can dump the contents of route_parameters->get('txtfile')
    };

You can use abbreviations for content types. For instance:

    get '/svg/:id' => sub {
        content_type 'svg';

        # here we can dump the image with id route_parameters->get('id')
    };

Note that if you want to change the default content-type for every route,
it is easier to change the C<content_type> setting instead.

=head2 context

Deprecated. Use L</app> instead.

=head2 dance

Alias for the C<start> keyword. L</to_app> is preferable.

=head2 dancer_app

Returns the app object. See L</app>.

=head2 dancer_version

Returns the version of Dancer. If you need the major version, do something
like:

    int(dancer_version);

or (better), call C<dancer_major_version>.

=head2 dancer_major_version

Returns the major version of Dancer.

=head2 debug

Logs a message of debug level:

    debug "This is a debug message";

See L<Dancer2::Core::Role::Logger> for details on how to configure where log
messages go.

=head2 decode_json ($string)

Deserializes a JSON structure from an UTF-8 binary string.

=head2 del

Defines a route for HTTP B<DELETE> requests to the given URL:

    del '/resource' => sub { ... };

You can also provide the route with a name:

    del 'rec' => '/resource' => sub { ... };

See C<uri_for_route> on how this can be used.

=head2 delayed

Stream a response asynchronously. For more information, please see 
L<Dancer2::Manual/Delayed responses (Async/Streaming)>, or 
L<this article|https://advent.perldancer.org/2020/22> in the 2020 Dancer 
Advent Calendar.

=head2 dirname

Returns the dirname of the path given:

    my $dir = dirname($some_path);

=head2 done

Close the streaming connection. Can only be called within a streaming 
response callback.

=head2 dsl

Allows access to the DSL within your plugin/application. Is an instance of
L<Dancer2::Core::DSL>.

=head2 encode_json ($structure)

Serializes a structure to a UTF-8 binary JSON string.

Calling this function will B<not> trigger the serialization's hooks.

=head2 engine

Given a namespace, returns the current engine object

    my $template_engine = engine 'template';
    my $html = $template_engine->apply_renderer(...);
    $template_engine->apply_layout($html);

=head2 error

Logs a message of error level:

    error "This is an error message";

See L<Dancer2::Core::Role::Logger> for details on how to configure where log
messages go.

=head2 false

Constant that returns a false value (0).

=head2 flush

Flush headers when streaming a response. Necessary when L</content> is called
multiple times.

=head2 forward

Runs an "internal redirect" of the current route to another route. More
formally; when C<forward> is executed, the current dispatch of the route is
aborted, the request is modified (altering query params or request method),
and the modified request following a new route is dispatched again. Any
remaining code (route and hooks) from the current dispatch will never be run
and the modified route's dispatch will execute hooks for the new route normally.

It effectively lets you chain routes together in a clean manner.

    get '/demo/articles/:article_id' => sub {

        # you'll have to implement this next sub yourself :)
        change_the_main_database_to_demo();

        forward "/articles/" . route_parameters->get('article_id');
    };

In the above example, the users that reach I</demo/articles/30> will
actually reach I</articles/30> but we've changed the database to demo
before.

This is pretty cool because it lets us retain our paths and offer a demo
database by merely going to I</demo/...>.

You'll notice that in the example we didn't indicate whether it was B<GET>
or B<POST>. That is because C<forward> chains the same type of route the
user reached. If it was a B<GET>, it will remain a B<GET> (but if you do
need to change the method, you can do so; read on below for details.)

Also notice that C<forward> only redirects to a new route. It does not redirect
the requests involving static files. This is because static files are handled
before L<Dancer2> tries to match the request to a route - static files take
higher precedence.

This means that you will not be able to C<forward> to a static file. If you
wish to do so, you have two options: either redirect (asking the browser to
make another request, but to a file path instead) or use C<send_file> to
provide a file.

B<WARNING:> Any code after a C<forward> is ignored, until the end of the
route. It's not necessary to use C<return> with C<forward> anymore.

    get '/foo/:article_id' => sub {
        if ($condition) {
            forward "/articles/" . route_parameters->get('article_id');
            # The following code WILL NOT BE executed
            do_stuff();
        }

        more_stuff();
    };

Note that C<forward> doesn't parse GET arguments. So, you can't use
something like:

    forward '/home?authorized=1';

But C<forward> supports an optional hashref with parameters to be added to
the actual parameters:

    forward '/home', { authorized => 1 };

Finally, you can add some more options to the C<forward> method, in a third
argument, also as a hashref. That option is currently only used to change
the method of your request. Use with caution.

    forward '/home', { auth => 1 }, { method => 'POST' };

=head2 from_dumper ($structure)

Deserializes a Data::Dumper structure.

=head2 from_json ($string, \%options)

Deserializes a JSON structure from a string. You should probably use
C<decode_json> which expects a UTF-8 encoded binary string and
handles decoding it for you.

=head2 from_yaml ($structure)

Deserializes a YAML structure.

=head2 get

Defines a route for HTTP B<GET> requests to the given path:

    get '/' => sub {
        return "Hello world";
    }

Note that a route to match B<HEAD> requests is automatically created as well.

You can also provide the route with a name:

    get 'index' => '/' => sub {
        return "Hello world";
    }

See C<uri_for_route> on how this can be used.

=head2 halt

Sets a response object with the content given.

When used as a return value from a hook, this breaks the execution flow and
renders the response immediately:

    hook before => sub {
        if ($some_condition) {
            halt("Unauthorized");

            # this code is not executed
            do_stuff();
        }
    };

    get '/' => sub {
        "hello there";
    };

B<WARNING:> Issuing a halt immediately exits the current route, and performs
the halt. Thus, any code after a halt is ignored, until the end of the route.
Hence, it's not necessary anymore to use C<return> with halt.

=head2 header

Deprecated. Use L</response_header> instead.

=head2 headers

Deprecated. Use L</response_headers> instead.

=head2 hook

Adds a hook at some position. For example :

  hook before_serializer => sub {
    my $content = shift;
    ...
  };

There can be multiple hooks assigned to a given position, and each will be
executed in order.

See L<Dancer2::Manual/HOOKS> for a list of available hooks.

=head2 info

Logs a message of C<info> level:

    info "This is an info message";

See L<Dancer2::Core::Role::Logger> for details on how to configure where log
messages go.

=head2 log

Logs messages at the specified level. For example:

    log( debug => "This is a debug message." );

=head2 mime

Shortcut to access the instance object of L<Dancer2::Core::MIME>. You should
read the L<Dancer2::Core::MIME> documentation for full details, but the most
commonly-used methods are summarized below:

    # set a new mime type
    mime->add_type( foo => 'text/foo' );

    # set a mime type alias
    mime->add_alias( f => 'foo' );

    # get mime type for an alias
    my $m = mime->for_name( 'f' );

    # get mime type for a file (based on extension)
    my $m = mime->for_file( "foo.bar" );

    # get current defined default mime type
    my $d = mime->default;

    # set the default mime type using config.yml
    # or using the set keyword
    set default_mime_type => 'text/plain';

=head2 options

Defines a route for HTTP B<OPTIONS> requests to the given URL:

    options '/resource' => sub { ... };

=head2 param

I<This method should be called from a route handler>.
This method is an accessor to the parameters hash table.

   post '/login' => sub {
       my $username = param "user";
       my $password = param "pass";
       # ...
   };

We now recommend using one of the specific keywords for parameters
(C<route_parameters>, C<query_parameters>, and C<body_parameters>)
instead of C<params> or C<param>.

=head2 params

I<This method should be called from a route handler>.
It's an alias for the L<Dancer2::Core::Request params
accessor|Dancer2::Core::Request/"params($source)">. It returns a hash (in
list context) or a hash reference (in scalar context) to all defined
parameters. Check C<param> below to access quickly to a single parameter
value.

    post '/login' => sub {
        # get all parameters as a single hash
        my %all_parameters = params;

        // request all parmameters from a specific source: body, query, route
        my %body_parameters  = params('body');
        my %route_parameters = params('route');
        my %query_parameters = params('query');

        # any $source that is not body, query, or route generates an exception
        params('fake_source'); // Unknown source params "fake_source"
    };

We now recommend using one of the specific keywords for parameters
(C<route_parameters>, C<query_parameters>, and C<body_parameters>)
instead of C<params> or C<param>.

=head2 pass

I<This method should be called from a route handler>.
Tells Dancer2 to pass the processing of the request to the next matching
route.

B<WARNING:> Issuing a pass immediately exits the current route, and performs
the pass. Thus, any code after a pass is ignored, until the end of the
route. Hence, it's not necessary anymore to use C<return> with pass.

    get '/some/route' => sub {
        if (...) {
            # we want to let the next matching route handler process this one
            pass(...);

            # this code will be ignored
            do_stuff();
        }
    };

B<WARNING:> You cannot set the content before passing and have it remain,
even if you use the C<content> keyword or set it directly in the response
object.

=head2 patch

Defines a route for HTTP B<PATCH> requests to the given URL:

    patch '/resource' => sub { ... };

(C<PATCH> is a relatively new and not-yet-common HTTP verb, which is
intended to work as a "partial-PUT", transferring just the changes; please
see L<RFC5789|http://tools.ietf.org/html/rfc5789> for further details.)

You can also provide the route with a name:

    patch 'rec' => '/resource' => sub { ... };

See C<uri_for_route> on how this can be used.

=head2 path

Concatenates multiple paths together, without worrying about the underlying
operating system:

    my $path = path(dirname($0), 'lib', 'File.pm');

It also normalizes (cleans) the path aesthetically. It does not verify whether
the path exists, though.

=head2 post

Defines a route for HTTP B<POST> requests to the given URL:

    post '/' => sub {
        return "Hello world";
    }

You can also provide the route with a name:

    post 'index' => '/' => sub {
        return "Hello world";
    }

See C<uri_for_route> on how this can be used.

=head2 prefix

Defines a prefix for each route handler, like this:

    prefix '/home';

From here, any route handler is defined to /home/*:

    get '/page1' => sub {}; # will match '/home/page1'

You can unset the prefix value:

    prefix undef;
    get '/page1' => sub {}; # will match /page1

For a safer alternative you can use lexical prefix like this:

    prefix '/home' => sub {
        ## Prefix is set to '/home' here

        get ...;
        get ...;
    };
    ## prefix reset to the previous version here

This makes it possible to nest prefixes:

   prefix '/home' => sub {
       ## some routes

      prefix '/private' => sub {
         ## here we are under /home/private...

         ## some more routes
      };
      ## back to /home
   };
   ## back to the root

B<Notice:> Once you have a prefix set, do not add a caret to the regex:

    prefix '/foo';
    get qr{^/bar} => sub { ... } # BAD BAD BAD
    get qr{/bar}  => sub { ... } # Good!

=head2 prepare_app

You can introduce code you want to run when your app is loaded, similar to the
C<prepare_app> in L<Plack::Middleware>.

    prepare_app {
        my $app = shift;

        ... # do your thing
    };

You should not close over the App instance, since you receive it as a first
argument. If you close over it, you B<will> have a memory leak.

    my $app = app();

    prepare_app {
        do_something_with_app($app); # MEMORY LEAK
    };

=head2 psgi_app

Provides the same functionality as L</to_app> but uses the deprecated
Dispatcher engine. You should use L</to_app> instead.

=head2 push_header

Deprecated. Use C<push_response_header> instead.

=head2 push_response_header

Do the same as C<response_header>, but allow for multiple headers with the same
name.

    get '/send/header', sub {
        push_response_header 'x-my-header' => '1';
        push_response_header 'x-my-header' => '2';
        # will result in two headers "x-my-header" in the response
    }

=head2 put

Defines a route for HTTP B<PUT> requests to the given URL:

    put '/resource' => sub { ... };

You can also provide the route with a name:

    put 'rec' => '/resource' => sub { ... };

See C<uri_for_route> on how this can be used.

=head2 query_parameters

Returns a L<Hash::MultiValue> object from the request parameters.

    /?foo=hello
    get '/' => sub {
        my $name = query_parameters->get('foo');
    };

    /?name=Alice&name=Bob
    get '/' => sub {
        my @names = query_parameters->get_all('name');
    };

=head2 redirect

Generates a HTTP redirect (302). You can either redirect to a complete
different site or within the application:

    get '/twitter', sub {
        redirect 'http://twitter.com/me';
        # Any code after the redirect will not be executed.
    };

B<WARNING:> Issuing a C<redirect> immediately exits the current route.
Thus, any code after a C<redirect> is ignored, until the end of the route.
Hence, it's not necessary anymore to use C<return> with C<redirect>.

You can also force Dancer to return a specific 300-ish HTTP response code:

    get '/old/:resource', sub {
        redirect '/new/' . route_parameters->get('resource'), 301;
    };

=head2 request

Returns a L<Dancer2::Core::Request> object representing the current request.

See the L<Dancer2::Core::Request> documentation for the methods you can
call, for example:

    request->referer;         # value of the HTTP referer header
    request->remote_address;  # user's IP address
    request->user_agent;      # User-Agent header value

=head2 request_data

Returns the request's body in data form
(in case a serializer is set, it will be in deserialized).

This allows us to distinguish between C<body_parameters>, a representation
of request parameters (L<Hash::MultiValue>) and other forms of content.

=head2 request_header

Returns request header(s).

    get '/get/headers' => sub {
        my $xfoo = request_header 'X-Foo';
        ...
    };

=head2 response

Returns the current response object, which is of type 
L<Dancer2::Core::Route::REQUEST>.

=head2 response_header

Adds a custom header to response:

    get '/send/header', sub {
        response_header 'x-my-header' => 'shazam!';
    }

Note that it will overwrite the old value of the header, if any. To avoid
that, see L</push_response_header>.

=head2 response_headers

Adds custom headers to response:

    get '/send/headers', sub {
        response_headers 'X-Foo' => 'bar', 'X-Bar' => 'foo';
    }

=head2 route_parameters

Returns a L<Hash::MultiValue> object from the route parameters.

    # /hello
    get '/:foo' => sub {
        my $foo = route_parameters->get('foo');
    };

=head2 runner

Returns the runner singleton. Type is L<Dancer2::Core::Runner>.

=head2 send_as

Allows the current route handler to return specific content types to the
client using either a specified serializer or as html.

Any Dancer2 serializer may be used. The specified serializer class will
be loaded if required, or an error generated if the class can not be found.
Serializer configuration may be added to your apps C<engines> configuration.

If C<html> is specified, the content will be returned assuming it is HTML with
appropriate C<Content-Type> headers and encoded using the apps configured
C<charset> (or UTF-8).

    set serializer => 'YAML';
    set template   => 'TemplateToolkit';

    # returns html (not YAML)
    get '/' => sub { send_as html => template 'welcome.tt' };

    # return json (not YAML)
    get '/json' => sub {
        send_as JSON => [ some => { data => 'structure' } ];
    };

C<send_as> uses L</send_file> to return the content immediately. You may
pass any option C<send_file> supports as an extra option. For example:

    # return json with a custom content_type header
    get '/json' => sub {
        send_as JSON => [ some => { data => 'structure' } ],
                { content_type => 'application/json; charset=UTF-8' },
    };

B<WARNING:> Issuing a send_as immediately exits the current route, and
performs the C<send_as>. Thus, any code after a C<send_as> is ignored,
until the end of the route. Hence, it's not necessary to use C<return>
with C<send_as>.

    get '/some/route' => sub {
        if (...) {
            send_as JSON => $some_data;

            # this code will be ignored
            do_stuff();
        }
    };

=head2 send_error

Returns a HTTP error. By default the HTTP code returned is 500:

    get '/photo/:id' => sub {
        if (...) {
            send_error("Not allowed", 403);
        } else {
           # return content
        }
    }

B<WARNING:> Issuing a send_error immediately exits the current route, and
performs the C<send_error>. Thus, any code after a C<send_error> is ignored,
until the end of the route. Hence, it's not necessary anymore to use C<return>
with C<send_error>.

    get '/some/route' => sub {
        if (...) {
            # Something bad happened, stop immediately!
            send_error(..);

            # this code will be ignored
            do_stuff();
        }
    };

=head2 send_file

Lets the current route handler send a file to the client. Note that the path
of the file must be relative to the B<public> directory unless you use the
C<system_path> option (see below).

    get '/download/:file' => sub {
        return send_file(route_parameters->get('file'));
    }

B<WARNING:> Issuing a C<send_file> immediately exits the current route, and
performs the C<send_file>. Thus, any code after a C<send_file> is ignored,
until the end of the route. Hence, it's not necessary anymore to use C<return>
with C<send_file>.

    get '/some/route' => sub {
        if (...) {
            # OK, send her what she wants...
            send_file(...);

            # this code will be ignored
            do_stuff();
        }
    };

C<send_file> will use PSGI streaming if the server supports it (most, if
not all, do). You can explicitly disable streaming by passing
C<streaming =E<gt> 0> as an option to C<send_file>.

    get '/download/:file' => sub {
        send_file( route_parameters->get('file'), streaming => 0 );
    }

The content-type will be set depending on the current MIME types definition
(see C<mime> if you want to define your own).

If your filename does not have an extension, you are passing in a filehandle,
or you need to force a specific mime type, you can pass it to C<send_file>
as follows:

    send_file(route_parameters->get('file'), content_type => 'image/png');
    send_file($fh, content_type => 'image/png');

Also, you can use your aliases or file extension names on C<content_type>,
like this:

    send_file(route_parameters->get('file'), content_type => 'png');

The encoding of the file or filehandle may be specified by passing both
the C<content_type> and C<charset> options. For example:

    send_file($fh, content_type => 'text/csv', charset => 'utf-8' );

For files outside your B<public> folder, you can use the C<system_path>
switch. Just bear in mind that its use needs caution as it can be dangerous.

   send_file('/etc/passwd', system_path => 1);

If you have your data in a scalar variable, C<send_file> can be useful as
well. Pass a reference to that scalar, and C<send_file> will behave as if
there was a file with that contents:

   send_file( \$data, content_type => 'image/png' );

Note that Dancer is unable to guess the content type from the data contents.
Therefore you might need to set the C<content_type> properly. For this kind
of usage an attribute named C<filename> can be useful. It is used as the
Content-Disposition header, to hint the browser about the filename it should
use.

   send_file( \$data, content_type => 'image/png'
                      filename     => 'onion.png' );

By default the Content-Disposition header uses the "attachment" type, which
triggers a "Save" dialog in some browsers. Supply a C<content_disposition>
attribute of "inline" to have the file displayed inline by the browser.

=head2 session

Provides access to all data stored in the user's session (if any).

It can also be used as a setter to store data in the session:

    # getter example
    get '/user' => sub {
        if (session('user')) {
            return "Hello, ".session('user')->name;
        }
    };

    # setter example
    post '/user/login' => sub {
        ...
        if ($logged_in) {
            session user => $user;
        }
        ...
    };

You may also need to clear a session:

    # destroy session
    get '/logout' => sub {
        ...
        app->destroy_session;
        ...
    };

If you need to fetch the session ID being used for any reason:

    my $id = session->id;

=head2 set

Defines a setting:

    set something => 'value';

You can set more than one value at once:

    set something => 'value', otherthing => 'othervalue';

=head2 setting

Returns the value of a given setting:

    setting('something'); # 'value'

=head2 splat

Returns the list of captures made from a route handler with a route pattern
which includes wildcards:

    get '/file/*.*' => sub {
        my ($file, $extension) = splat;
        ...
    };

There is also the extensive splat (A.K.A. "megasplat"), which allows
extensive greedier matching, available using two asterisks. The additional
path is broken down and returned as an arrayref:

    get '/entry/*/tags/**' => sub {
        my ( $entry_id, $tags ) = splat;
        my @tags = @{$tags};
    };

The C<splat> keyword in the above example for the route F</entry/1/tags/one/two>
would set C<$entry_id> to C<1> and C<$tags> to C<['one', 'two']>.

=head2 start

Starts the application or the standalone server (depending on the deployment
choices).

This keyword should be called at the very end of the script, once all routes
are defined. At this point, Dancer2 takes over.

Prefer L</to_app> instead of C<start>.

=head2 status

Changes the status code provided by an action. By default, an action will
produce an C<HTTP 200 OK> status code, meaning everything is OK:

    get '/download/:file' => {
        if (! -f route_parameters->get('file')) {
            status 'not_found';
            return "File does not exist, unable to download";
        }
        # serving the file...
    };

In that example, Dancer will notice that the status has changed, and will
render the response accordingly.

The C<status> keyword receives either a numeric status code or its name in
lower case, with underscores as a separator for blanks - see the list in
L<Dancer2::Core::HTTP/"HTTP CODES">. As an example, The above call translates
to setting the code to C<404>.

=head2 template

Returns the response of processing the given template with the given
parameters (and optional settings), wrapping it in the default or specified
layout too, if layouts are in use.

An example of a  route handler which returns the result of using template to
build a response with the current template engine:

    get '/' => sub {
        ...
        return template 'some_view', { token => 'value'};
    };

Note that C<template> simply returns the content, so when you use it in a
route handler, if execution of the route handler should stop at that point,
make sure you use C<return> to ensure your route handler returns the content.

Since C<template> just returns the result of rendering the template, you can
also use it to perform other templating tasks, e.g. generating emails:

    post '/some/route' => sub {
        if (...) {
            email {
                to      => 'someone@example.com',
                from    => 'foo@example.com',
                subject => 'Hello there',
                msg     => template('emails/foo', { name => body_parameters->get('name') }),
            };

            return template 'message_sent';
        } else {
            return template 'error';
        }
    };

Compatibility notice: C<template> was changed in version 1.3090 to
immediately interrupt execution of a route handler and return the content,
as it's typically used at the end of a route handler to return content.
However, this caused issues for some people who were using C<template> to
generate emails etc, rather than accessing the template engine directly, so
this change has been reverted in 1.3091.

The first parameter should be a template available in the views directory,
the second one (optional) is a hashref of tokens to interpolate, and the
third (again optional) is a hashref of options.

For example, to disable the layout for a specific request:

    get '/' => sub {
        template 'index', {}, { layout => undef };
    };

Or to request a specific layout, of course:

    get '/user' => sub {
        template 'user', {}, { layout => 'user' };
    };

Some tokens are automatically added to your template (C<perl_version>,
C<dancer_version>, C<settings>, C<request>, C<vars> and, if you
have sessions enabled, C<session>). Check L<Default Template
Variables|Dancer2::Manual/Default-Template-Variables>
for further details.

=head2 to_app

Returns the PSGI coderef for the current (and only the current) application.

You can call it as a method on the class or as a DSL:

    my $app = MyApp->to_app;

    # or

    my $app = to_app;

There is a
L<Dancer Advent Calendar article|http://advent.perldancer.org/2014/9> covering
this keyword and its usage further.

=head2 to_dumper ($structure)

Serializes a structure with Data::Dumper.

Calling this function will B<not> trigger the serialization's hooks.

=head2 to_json ($structure, \%options)

Serializes a structure to JSON. You should probably use C<encode_json> instead
which handles encoding the result for you.

=head2 to_yaml ($structure)

Serializes a structure to YAML.

Calling this function will B<not> trigger the serialization's hooks.

=head2 true

Constant that returns a true value (1).

=head2 upload

Provides access to file uploads. Any uploaded file is accessible as a
L<Dancer2::Core::Request::Upload> object. You can access all parsed uploads
via:

    post '/some/route' => sub {
        my $file = upload('file_input_foo');
        # $file is a Dancer2::Core::Request::Upload object
    };

If you named multiple inputs of type "file" with the same name, the C<upload>
keyword would return an Array of L<Dancer2::Core::Request::Upload> objects:

    post '/some/route' => sub {
        my ($file1, $file2) = upload('files_input');
        # $file1 and $file2 are Dancer2::Core::Request::Upload objects
    };

You can also access the raw hashref of parsed uploads via the current
C<request> object:

    post '/some/route' => sub {
        my $all_uploads = request->uploads;
        # $all_uploads->{'file_input_foo'} is a Dancer2::Core::Request::Upload object
        # $all_uploads->{'files_input'} is an arrayref of Dancer2::Core::Request::Upload objects
    };

Note that you can also access the filename of the upload received via the
C<body_parameters> keyword:

    post '/some/route' => sub {
        # body_parameters->get('files_input') is the filename of the file uploaded
    };

See L<Dancer2::Core::Request::Upload> for details about the interface provided.

=head2 uri_for

Returns a fully-qualified URI for the given path:

    get '/' => sub {
        redirect uri_for('/path');
        # can be something like: http://localhost:5000/path
    };

Query string parameters can be provided by passing a hashref as a second param:

    uri_for('/path', { foo => 'bar' });
    # would return e.g. http://localhost:5000/path?foo=bar

By default, the parameters will be URL encoded:

    uri_for('/path', { foo => 'hope;faith' });
    # would return http://localhost:5000/path?foo=hope%3Bfaith

If desired (for example, if you've already encoded your query
parameters and you want to prevent double encoding) you can disable
URL encoding via a third parameter:

    uri_for('/path', { foo => 'qux%3Dquo' }, 1);
    # would return http://localhost:5000/path?foo=qux%3Dquo

=head2 uri_for_route

An enhanced version of C<uri_for> that utilizes routes' names.

    get 'view_entry' => '/entry/view/:id' => sub {...};

Now that the route has a name we can use C<uri_for_route> to
create a URI for it:

    my $path = uri_for_route(
        'view_entry',
        { 'id'  => 3 },
        { 'foo' => 'bar' },
    );

    # (assuming it's run on a local server in HTTP port 5000)
    # $path = 'http://localhost:5000/entry/view/3?foo=bar'

This works for every HTTP method, except C<HEAD> (which is
effectively a C<GET>).

It can also be used in templates:

    <!-- some_template.tt -->
    [% request.uri_for_route( 'my_route_name', { 'foo' => 'bar' }, { 'id' => 4 } ) %]

There are multiple arguments options:

=over 4

=item * Route parameters

The first argument controls the route parameters:

    get 'test' => '/:foo/:bar' => sub {1};
    # ...
    $path = uri_for_route( 'test', { 'foo' => 'hello', 'bar' => 'world' } );
    # $path = http://localhost:5000/hello/world

=item * Splat route parameters

If you provide an arrayref instead of hashref, it will assume on
these being splat and megasplat args:

    get 'test' => '/*/*/**' => sub {1};
    # ...
    $path = uri_for_route(
        'test',
        [ 'hello', 'world', [ 'myhello', 'myworld' ],
    );
    # $path = http://localhost:5000/hello/world/myhello/myworld

=item * Mixed route parameters

If you have a route that includes both, the splat and megasplat
arguments need to be under the C<splat> key:

    patch 'test' => '/*/:id/*/:foo/*' => sub {1};
    # ...
    $path = uri_for_route(
        'test',
        {
            'id'    => 4,
            'foo  ' => 'bar',
            'splat' => [ 'hello', 'world' ],
        }
    );
    # $path = http://localhost:5000/hello/4/world/bar

=item * Query parameters

If you want to create a path the query parameters, use the
second argument:

    get 'index'       => '/:foo' => sub {1};
    get 'update_form' => '/update' => sub {1};

    # ...

    $path = uri_for_route(
        'index',
        { 'foo' => 'bar' },
        { 'id'  => 1 },
    );
    # $path = http://localhost:5000/bar?id=1

    $path = uri_for_route( 'update_form', {}, { 'id' => 2 } );
    # $path = http://localhost:5000/update?id=2

(Technically, only C<GET> requests should include query parameters, but
C<uri_for_route> does not enforce this.)

=item * Disable URI escaping

The final parameter determines whether the URI will be URI-escaped or not:

    get 'show_entry' => '/view/:str_id' => sub {1};
    # ...
    $path = uri_for_route(
        'show_entry',
        { 'str_id' => '<javascript>...' },
        {},
    );
    # $path = http://localhost/view/%3Cjavascript%3E...

This is useful when your ID is not HTML-safe and might include HTML
tags and Javascript code or include characters that interfere with the
URI request string (like a forward slash).

This is on by default, but you can disable it by setting this flag:

    get 'show_entry' => '/view/:str_id' => sub {1};
    # ...
    $path = uri_for_route(
        'show_entry',
        { 'str_id' => '<javascript>...' },
        {},
        1,
    );
    # $path = http://localhost/view/<javascript>...

=back

=head2 var

Provides an accessor for variables shared between hooks and route
handlers. Given a key/value pair, it sets a variable:

    hook before => sub {
        var foo => 42;
    };

Later, route handlers and other hooks will be able to read that variable:

    get '/path' => sub {
        my $foo = var 'foo';
        ...
    };

=head2 vars

Returns the hashref of all shared variables set during the hook/route
chain with the C<var> keyword:

    get '/path' => sub {
        if (vars->{foo} eq 42) {
            ...
        }
    };

=head2 warning

Logs a warning message through the current logger engine:

    warning "This is a warning";

See L<Dancer2::Core::Role::Logger> for details on how to configure where log
messages go.

=head1 AUTHOR

Dancer Core Developers

=head1 COPYRIGHT AND LICENSE

This software is copyright (c) 2023 by Alexis Sukrieh.

This is free software; you can redistribute it and/or modify it under
the same terms as the Perl 5 programming language system itself.

=cut